Preparation of Tritiated Opioid Peptides In 1996, Multiple Peptide Systems (MPS) was awarded a National Institute on Drug Addiction contract (NOIDA-1-7302) to provide their associated researchers with highly purified opioid peptides and other centrally active neuropeptides. The contract in part includes the preparation and purification of labeled peptides having high specific activity at desired locations. Most of these compounds are not commercially available. The NIDA associated researchers are from private, academic and governmental research entities who obtain NIDA research grants in which they are given the opportunity to obtain the unique tritiated neuropeptides. In order to facilitate the production of these unique peptides, MPS has contracted the use of the National Tritium Labelling Facility at the Lawrence Berkeley National Laboratory. The extensive laboratory facilities at the NTLF allow for higher quality compounds than those few products that are commercially available. With the specialized equipment and the knowledgeable employees, the facility is an excellent tool to permit labeling, purification and characterization of the tritium labeled compounds to be accomplished in a rapid, economical, and safe manner. Special precursors having either a labile halogen atom or a reactive double bond are prepared and purified at MPS. The precursor is dissolved in DMF. After addition of Palladium (II) oxide as catalyst, the slurry is held in contact with tritium gas for 4 hours in the NTLF tritium reaction TITLE: Preparation of Tritiated Opioid Peptides (Continued) manifold. After recovery of the excess tritium and filtering of catalyst, the labeled peptide in solution is analyzed by liquid scintillation to check for activity. Afterwards, the newly tritiated compounds are purified to greater than 90% using preparative RP-HPLC with an in-line tritium beta counter detector. Tritium incorporation into the compound structure is checked by tritium NMR, which also gives an analysis tool for specific activity. The labeled peptides usually have a specific activities ranging from 40 Ci/mmol to 55 Ci/mmol. The compounds are mainly used for research focusing on receptor characterization, metabolism studies (ADME: adsorption, distribution, metabolism and excretion) and new active compounds identification (agonist or antagonist). Results from this research have dire ct a pplic atio n, as an example, in the devel opment of unique analgesic drug s.